1. Field of the Invention
The present invention relates to a drill set for a dental screw implant fixture with a self-tap. When treating a lost tooth part to recover lost function, the drill set is used for forming and finally adjusting an implant hole in a jawbone at the lost tooth location. A dental screw implant fixture having a self-tapping function at a tip end thereof is implanted where the tooth was lost.
2. Description of the Conventional Art
To treat lost teeth, a technique using a bridge and a technique using a denture has been generally practiced.
However, in the technique using a bridge, healthy natural teeth on both sides of the lost tooth are cut to form piers, and a dental prosthesis positioned at the lost tooth area is fixed between metallic members engaged and fixed on the piers. Therefore, not only healthy natural teeth must be cut for providing the piers, but also the process has a disadvantage in that an occlusion pressure is not directly applied to the inside of the oral cavity at the dental prosthesis positioned at the lost tooth area. Thus, bone resorption occurs in that area.
In the technique using a denture, a dental prosthesis is used that is formed by fixing an artificial tooth on a denture plate formed with a synthetic resin or the like. In this technique, because occlusion pressure is applied to the dental prosthesis bore by remaining natural teeth and/or the oral mucosa adjacent to the denture, there are some cases where uncomfortable feeling is caused during use. Accordingly, gustatory acceptors scattered in the tissue of the oral mucosa are covered with the denture plate to blunt gustation. Another disadvantage is that resorption of an alveolar ridge occurs upon using a prolonged period.
As a result of finding that metallic titanium is favorably bonded to bone, the following dental implant technique has been developed and practiced as a therapy for solving the problems. That is, as employing the “osseointegration”, a dental implant fixture formed with metallic titanium to be a pier of a dental prosthesis is implanted in an implant hole formed at the lost tooth location to exert the function of a dental root of a natural tooth. A dental prosthesis is connected and fixed on the oral cavity side of the dental implant fixture.
In the remedy using the dental implant, because a dental prosthesis can be fixed without covering the oral mucosa, a natural tooth feel can be obtained without occurrence of unfavorable feeling and blunting of gustation upon wearing the dental prosthesis. Furthermore, an advantage is also obtained in that an appropriate occlusion force is applied to the jawbone, so as to suppress to a minimum level the bone resorption which might occur assuming that no dental implant fixture is implanted. Therefore, remedies using a dental implant are being rapidly developed and are being applied to loss of a sole tooth, local loss of two or more teeth, and an anodont jawbone (whole teeth loss).
The part of the dental implant fixture, which is implanted in the implant hole formed in the jawbone at the lost tooth location assuming the osseointegration, used in the dental implant remedy is generally formed into such a shape that is substantially equivalent to a tooth root. The surface shape thereof is, for example, a cylindrical shape (disclosed, for example, in FIGS. 1 and 3 of JP-A-7-80002) and a screw shape formed by providing a male screw on a cylindrical part of a body of a straight dental implant fixture (disclosed, for example, in FIG. 1 of JP-A-10-211218). Upon implanting the cylindrical dental implant fixture into a jawbone, an implant hole having a diameter equivalent to or slightly smaller than the diameter of the cylindrical part of the body of the cylindrical dental implant fixture is formed in the jawbone. The cylindrical dental implant fixture is pressed into the implant hole by hitting. However, there are disadvantages in that it is difficult to ensure stable fixation upon implanting due to difficulty in forming an accurate implant hole and difficulty in adjustment of an allowance for press fitness corresponding to the property of the bone. Additionally, a large burden is applied to a patient.
On the other hand, upon implanting the screw dental implant fixture in a jawbone, an implant hole having a diameter that is substantially equivalent to a root diameter of the male screw provided on the dental implant fixture is provided in the jawbone, and in general, a female screw capable of being screwed with the male screw provided on the screw dental implant fixture is provided on the implant hole with a tap. This is followed by screwing the screw dental implant fixture thereinto. Accordingly, there are some cases, depending on property of the bone, where difficulty occurs upon providing such a female thread on the implant hole that enables stable fixation upon implanting. Therefore, a prolonged period of time is required to form the female screw in the implant hole. This can apply a large burden to a patient.
In order to solve the problems, several screw dental implant fixtures have been proposed (for example, in FIGS. 1 and 2 of JP-A-2001-321392, and JP-A-2001-512348) in which a self-tapping function is previously provided to the dental implant fixture, whereby it can be implanted while forming a female thread in the implant hole formed in the jawbone at the lost tooth part. The screw dental implant fixture with a self-tap has improved fixation after implanting, and simpler in operation owing to the formation of the female thread attained simultaneously with the implantation. Further, in order to provide, a space for housing cut chips of the jawbone upon cutting the female thread, and to improve the fixation by providing a taper shape similar to a tooth root on the tip end part of the male screw implanted in the implant hole. Such a dental implant fixture is being widely used that has a taper shape on the tip end of the male screw and has on the tip end a cutting blade and a concave part provided continuously with the cutting blade.
As a result, the stability of the dental implant fixture immediately after implanting into the implant hole formed in the jawbone at the lost tooth location (initial fixing property) is improved. Thus, such a remedy receives attention in that an occlusion pressure can be applied to the dental implant fixture immediately after the implantation of the dental implant fixture in the implant hole formed in the jawbone or in an earlier stage after the implantation.
However, a drill for forming and finally adjusting the implant hole in the jawbone at the lost tooth part for screw dental implant fixture with a self-tap has a chevron tip end and a cutting blade formed continuously thereto capable of forming a circular hole having a diameter that is substantially equivalent to the maximum root diameter of the screw dental implant fixture with a self-tap. Therefore, in the case where the implant hole is formed by using the drill to such a depth that is substantially equivalent to the length, with which the screw dental implant fixture with a self-tap is implanted, the taper part at the tip end of the screw dental implant fixture with a self-tap is not in contact with the jawbone. Thus the tip may be less stable upon fixation. In the case where, on the other hand, the implant hole is provided to such a length that corresponds to the starting point of the taper part at the tip end of the screw dental implant fixture with a self-tap, there are such disadvantages in that the cut amount of the jawbone with the cutting blade provided on the taper part at the tip end of the screw dental implant fixture with a self-tap is increased. Therefore, the cut chips of the jawbone cannot be housed in the concave part provided continuously with the cutting blade. Also, it fails to ensure the stability upon fixation by applying a suitable load to the ostein of the jawbone.